Present invention relates to an engine control system, especially relates to a compression igniting type engine control system.
A lean burn engine is widely known to let a lean air-fuel mixture burn as an effective means for enhancing efficiency of the engine.
The pumping loss becomes little by making the fuel burn leanly, because more air is inhaled to the engine when driving it with an equal torque.
In a gasoline engine used widely today, the air-fuel mixture is ignited with the spark plug, and the flame propagation can be attained.
However, the lean air-fuel mixture of the air fuel ratio such as 40 around is difficult to be ignited, and the burning becomes unstable.
Therefore the fuel is directly injected in a cylinder of the engine, and the air-fuel mixture is gathered near by the spark plug, thereby the good burning of the air-fuel mixture can be secured and it is used for the engine for the automobile.
The fuel consumption in such an in-cylinder fuel injection engine is enhanced, however as the fuel is injected in the cylinder, temperature of the inhaled air falls by vaporization of the fuel, air density becomes high, and there arise a merit too that can improve by charging efficiency. However, as the air-fuel mixture concentrates near around the spark plug, combustion temperature becomes high, and there arises a subject as that NOx is easy to increase.
In the lean burning of the homogeneous air-fuel mixture, as the rise of the combustion temperature can be restrained, NOx can be made low. However, as the igniting and the flame propagation are unstable, the air fuel ratio in the driving is limited under 23 around, and the fuel consumption enhancement are limited to 15%, too.
In Japanese Patent Laid-open No. 9-287527, a homogeneous air-fuel mixture is formed in the cylinder by intake port fuel injection, the lean mixture can be burn by a compression igniting. The fuel mixture is burned by not the spark ignition but the compression igniting, the igniting from many igniting sources becomes possible, the flame propagation distance is short, too, and insurance of ignitability, and rapid burning are realized. Because being a uniform air-fuel mixture, a large reduction of NOx is possible.
However when the torque increases (when quantities of the fuel is much), the burning pressure becomes high rapidly, knocking is generated, and there is a subject as that operation range is narrow. That is, a compulsion igniting means as spark ignition is not provided, the control of the igniting becomes difficult.
Making burning advanced by external EGR and controlling ignitability by controlling the intake temperature, are disclosed, a responsibility of the external EGR and the intake temperature control are so retarded, and a following characteristics is a problem, when the engine torque as in the automobile changes.
The first object of present invention, is to provide a system in which NOx is low and a fuel consumption can be improved in an engine having compression igniting mode, by making it possible to ignite the fuel in a large operation range by providing a fuel injection and by ultra-leanly burning the homogeneous air-fuel mixture.
The second object of the present invention is to improve an igniting controllability by an igniting trigger means.
In order to achieve the first object mentioned above, in the in-cylinder fuel injection engine driven with a compression igniting mode, a first fuel injection for controlling a initial combustion speed before igniting and a second injection for controlling an engine torque after that, are provided, ignitability can be balanced with a torque contrillability by increasing the second fuel injection ratio for the engine torque control according to the engine torque.
The second object of the present invention is to improve the igniting controllability by providing an igniting trigger means in an in-cylinder fuel injection engine having a compression igniting mode.
Any one of a microtron, a laser, an spark plug, EGR, compression ratio control means and a combination thereof is provided as the igniting trigger means, thereby the temperature of the air-fuel mixture is raised higher.
Moreover, a rich spot is formed in the homogeneous air-fuel mixture, and the air-fuel mixture that is easy to be ignited is formed.